Cervical plate with a feedback device for selective association with bone screw blocking mechanism

ABSTRACT

A bone plate having at least one screw hole adapted to receive a bone screw, a blocker having a blocking end for blocking a bone screw from further backout of bone the blocker being predisposed in a blocking position wherein the blocking end at least partially overlaps a portion of the screw hole, the blocker being moveable from the blocking position by contact with the bone screw during insertion of the bone screw into the screw hole, and a blocker fixation element having an open orientation at which the blocker can move from the blocking position and a closed orientation preventing substantial movement of the blocker from the blocking position. The blocker fixation element cannot be moved to the closed orientation unless the screw head passes the blocker, thereby revealing that the blocker fixation element is in position to prevent substantial movement of the blocker.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/535,738, filed on Nov. 7, 2014, now U.S. Pat. No. 9,351,775, which isa continuation of U.S. patent application Ser. No. 12/291,335, filed onNov. 7, 2008, now U.S. Pat. No. 8,906,077, which claims the benefit ofthe filing date of U.S. Provisional Patent Application No. 61/002,486,filed Nov. 9, 2007, and entitled “CERVICAL PLATE WITH A FEEDBACK DEVICEFOR SELECTIVE ASSOCIATION WITH BONE SCREW BLOCKING MECHANISM,” thedisclosures of which are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention generally relates to a bone plate having a screwblocking mechanism. More particularly, the present invention relates toa cervical bone plate having a screw blocking mechanism that can beactuated by a tool.

Bone plates and bone screws are often used in orthopedic applications.For instance, bone plates and bone screws are used in connection withthe stabilization or fusion of vertebral bodies in the spine, and arealso used in connection with trauma applications, for instance, infracture fixation. In many instances, there is concern that bone screwsmay loosen after implantation of a bone plate. To the extent that thisoccurs, it has been desirable to ensure that the screw does not fullyremove itself from the bone and bone plate. Many plate systems includemeans for affirmatively locking the bone screw upon implantation throughthe plate. In other instances, a blocking mechanism is employed.

A blocking mechanism does not affirmatively hold the screw in itsimplanted position upon implantation or lock the bone screw to theplate; rather, it merely serves to block an already loosening screw frombacking out any further from the plate.

Screw blocking mechanisms which are associated with the plate prior toinsertion of a bone screw are known. In some instances, such blockingmechanisms allow for the insertion of the bone screw via the resiliencyof the blocker itself. For example, a split ring may be housed in arecess in a bone screw receiving hall, such as that shown in U.S. Pat.No. 6,602,255.

It may be desirable to prevent expansion of a blocker after a bone screwand bone plate have been implanted. The present invention addresses thisdesirability.

SUMMARY OF THE INVENTION

The present invention may be practiced in one aspect by a bone platehaving a top surface and a bottom surface with at least one screw holetherethrough, a blocker having an end and being movable by insertion ofa bone screw into a blocking position such that the end is disposed overat least one bone screw hole and being movable by reason of the bonescrew being inserted into the bone plate and bone during implantation,and a cam having an open orientation at which the blocker is permittedto move and a close orientation at which the blocker is substantiallyprevented from moving from the blocking position. The cam in this aspectof the present invention cannot be moved to the closed orientationunless the bone screw head is disposed distally of the blocker.

In accordance with another aspect of the present invention, the abovebone plate is provided wherein the cam has a top surface and a bottomsurface with a camming surface. The camming surface in the closedorientation may be arranged against the blocker. The camming surface mayalso, in open orientation, be arranged away from the blocker. In anotheraspect of the present invention, the blocker makes contact with the bonescrew to lock the bone screw with respect to the plate uponimplantation. In one aspect of the invention, the blocker is orientedabove the bone screw, with no contact, such that it can only act as ablocker.

The above bone plate may also include a recess in which the blocker ispositioned. The cam may include a boss disposed within an aperture, theboss being rotatably engaged within the aperture such that the cam mayrotate from a closed orientation to an open orientation.

The blocking end of the blocker may be arcuate in shape such that itgenerally follows the arcuate shape of the bone screw hole. The arcuateshape of the blocking end may correspond to the arcuate shape of thebone screw hole, or may differ somewhat from the arcuate shape of thebone screw hole. In one aspect of the present invention, the blocker mayextend over the periphery of bone screw hole by about 25% of theperimeter. In another aspect, it is about ⅓ of the periphery. Of course,as long as the blocker can be moved upon the insertion of the bonescrew, the coverage on the perimeter of the bone screw hole may belarger.

In another aspect of the present invention, the bone plate is part of asystem that includes at least a bone screw, or preferably a bone screwfor each bone screw-receiving hole.

In connection with another aspect of the present invention, a method maybe employed practicing the steps of providing a plate having a blockerwhich extends over a portion of a bone screw receiving hole in a boneplate, inserting a bone screw through the bone screw receiving hole, andsimultaneously moving the blocker away from the screw hole to allowinsertion of the bone screw, continuing insertion until the bone screwpasses the blocker to allow the blocker to move back into the blockingposition, and manipulating the cam from an open orientation to a closedorientation at which movement of the blocker from the blocking positionis substantially prevented.

Yet a further aspect of the present invention may be practiced by a boneplate having a top surface and a lower surface and at least two bonescrew receiving holes therethrough, undercuts in the periphery of atleast a portion of the bone screw receiving holes, a blocker housedwithin the recess, the blocker having blocking ends which extend overportions of the respective bone screw receiving holes such that theblockers in a blocking position at which it is above a bone screw seatedin the plate and in a bone during implantation and can block the bonescrew from backing out of the bone plate should the bone screw loosen,the blocker being movable from the blocking position upon insertion ofthe respective bone screw, whereby the bone screw causes the blocker tomove away from the bone screw receiving hole to allow insertion untilthe bone screw passes the blocker and the blockers thereby permitted toreturn to the blocking position. In connection with this aspect of thepresent invention, the blocker may be seated in a recess which iscoextensive with the grooves around the least portion of the peripheryof the bone screw receiving holes, and the recess in the plate mayinclude a further groove opposition the bone screw receiving holes. Theaspect of the present invention may also include a blocker fixing devicewhich, after insertion of the bone screws in the bone plate and intobone, can be actuated by a surgeon to prevent the blocker from movingfrom the blocking position.

In another aspect of the present invention, a bone plate is provided,the bone plate having at least a pair of holes for receiving bone screwsduring implantation, a blocker associated with the plate and overlappinga portion of both the bone screw holes, a first blocker fixation elementassociated with a first bone screw hole and a second blocker fixationelement associated with a second bone screw hole, the first and secondblocker fixation elements being independently operable to selectivelylock the blocker in a position overlapping the respective screw hole. Inconnection with the aspect of the present invention, the blockerfixation elements may be rotatable devices having camming surfaces toengage a cam receiving surface on separate portions of the blocker.Effectively, a surgeon would be required to move each blocker fixationelement independently of the other blocker fixation elements after abone screw has been inserted through the plate and into bone such thatthe blocker cannot be moved from the blocking position as set forth inconnection with this or other previous aspects of the present invention.

In connection with another aspect of the present invention, a bone plateincludes at least one bone plate receiving hole and a recesscommunicating with the bone screw receiving hole, the recess including arotatable member that is movable between an open position at which abone screw can be inserted into the bone screws receiving hole and aclosed position at which the member overlays a portion of bone screwreceiving hole to block a bone screw from further backing out should thebone screw begin to back out after implantation. The member may includean opening which engages, in the closed position, a protrusion in therecess of the plate to lock the member in the blocking position.

In connection with another aspect of the present invention, a blockplate screw receiving hole, and a hinged member which is hingedablymovable between an open position and at which a bone screw could beinserted into the bone screw hole and a close position at which thehinged member is in a blocking position to overlay a portion of the holeand block a bone screw from further backing out should the bone screwbegin to back out of bone after implantation of the bone screw and thebone plate.

In connection with this aspect of the present invention, the hingedmember may include a flexible portion which facilitates locking of thehinged member in the blocking position following movement from the openposition and after a bone screw is inserted into the bone screw hole.

Another aspect of the present invention is similar to the foregoingexcept that the hinge member is hingedably connected to the plate in acentral opening between sets of bone screw receiving holes. The hingedmember would be closed to the blocking position after the bone screwshave been implanted, and the hinge member would overlay a portion of atleast two bone holes to block further backing out of the bone screws.The hinged member would have an opening to receive a projectionextending from the plate between the holes to thereby lock the hingemember in the blocking position after the bone screw holes areimplanted.

In connection with yet another embodiment of the present invention, abone plate has at least two holes, a blocking member positioned betweenthe two holes and being slideable along an axis of the plate such thatan enlarged portion of the blocking member extends over the holes toblock bone screws from further backing out after the bone screws havebeen implanted. The blocking member includes a slot in an arrow portionand is connected to the plate via the slot, there being a fixationmember allowing the blocking member to slide relative to an axis of theplate until the enlarged portion of the member overlays the holes, atwhich time the fixation member can be utilized to lock the blockingmember in the blocking position.

The present invention provides a plate system wherein the bone screw, ifloosened after implantation, is blocked from loosening beyond theblocker (alternatively, called the spring bar). The present inventionalso provides a blocking system wherein the blocker operates withoutrequiring further actuation beyond implanting the screw past theblocker. A secondary action of a cam is provided to ensure that themovement of the bone screw does not displace the blocker upon potentialbackout of the bone screw. The present invention further provides thesurgeon with a tactile and visual feedback as to the position of thebone screw. The feedback may result from the loss of the force exertedby the blocker on the head of the screw when the screw is tightened pastthe blocker. The feedback may include an audible click when the screwmoves past the blocker. The feedback may also result from visualobservation of the position of the blocker. The blocker may be coloredto enhance such visual feedback. The feedback also comes from thesecondary action of manipulating a feedback device, i.e., the cam. Thesimple secondary action of manipulating the cam being, in and of itself,a feedback to the surgeon, even beyond any tactile feedback from thecam.

One aspect the invention provides a bone plate having a top surface anda bottom surface and at least one screw hole adapted to receive a bonescrew. A flat is formed on the top surface of the bone plate, and atleast a portion of the flat borders the screw hole. A blocker isprovided, the blocker being adapted for insertion in the flat and havinga screw end and a base end. At least a portion of the screw end isshaped to match the periphery of the screw hole and projects over thescrew hole when the blocker is inserted in the flat. At least one leg isconnected to the screw end and extends towards the base end. The leg iscapable of elastic deflection. In use, when the screw is inserted in thescrew hole, a portion of the bone screw comes in contact with the screwend, and as the screw advances into the bone plate, the blocker isdeflected away to allow the screw head to move past the blocker, afterwhich the blocker projects over the screw head. The blocker may becolored. A cam may be rotated to secure the blocker in its blockingposition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a one-level bone plate system inaccordance with an embodiment of the present invention.

FIG. 2 is a perspective view of an end of a bone plate in accordancewith another embodiment of the present invention, the other end of thebone plate being a mirror image thereof.

FIG. 3 is another perspective view of the end of the bone plate as shownin FIG. 2.

FIG. 4 is a perspective view of a cam in accordance with an embodimentof the present invention.

FIG. 5 is a perspective view of a two-level bone plate system inaccordance with an embodiment of the present invention.

FIG. 6 is a perspective view of a bone plate in accordance with anotherembodiment of the present invention.

FIG. 7 is another perspective view of a central portion of the boneplate as shown in FIG. 6.

FIG. 8 is a perspective view of an end of a tool in accordance with anembodiment of the present invention.

FIG. 9 is a plan view of a handle of the tool in accordance with anotherembodiment of the present invention.

FIG. 10 is a plan view of a handle of the tool in accordance with afurther embodiment of the present invention.

FIG. 11 is a plan view of a handle of the tool in accordance with stillanother embodiment of the present invention.

FIG. 12 is a plan view of a handle of the tool in accordance withanother embodiment of the present invention.

FIG. 13 is a perspective view of a bone plate system in accordance witha further embodiment of the present invention.

FIG. 14 is another perspective view of one end of the bone plate asshown in FIG. 13.

FIG. 15 is a further perspective view of one end of the bone plate asshown in FIG. 13.

FIG. 16 is a perspective view of a bone plate system in accordance withstill a further embodiment of the present invention.

FIG. 17 is a perspective view of a bone plate system in a substantiallyopen position in accordance with another embodiment of the presentinvention.

FIG. 18 is a perspective view of the bone plate system of FIG. 17 in asubstantially closed position.

FIG. 19 is a perspective view of a bone plate system in a substantiallyopen position in accordance with yet another embodiment of the presentinvention.

FIG. 20 is a perspective view of the bone plate system of FIG. 19 in asubstantially closed position.

FIG. 21 is a perspective view of a cover according to still anotherembodiment of the present invention

FIG. 22 is a perspective view of a bone plate system having includingcover of FIG. 21.

FIG. 23 is another perspective view of the cover of FIG. 21.

FIG. 24 is a perspective view of the bone plate system of FIG. 22 in asubstantially open position.

FIG. 25 is a perspective view of the bone plate system of FIG. 22 in asubstantially closed position.

FIG. 26 is a perspective view of a bone plate system in accordance withyet another embodiment of the present invention.

FIG. 27 is a perspective view of a bone plate system in accordance withstill a further embodiment of the present invention.

FIG. 28 is a perspective view of a two-level bone plate system inaccordance with another embodiment of the present invention.

FIG. 29 is a perspective view of the underside of the cam and blocker ofthe bone plate system of FIG. 28.

FIG. 30 is a perspective view of a two-level bone plate system inaccordance with still another embodiment of the present invention.

DETAILED DESCRIPTION

In accordance with an embodiment of the present invention, FIG. 1depicts a one-level bone plate system 10 that may be used to stabilizeor fuse vertebral bodies in the cervical or other region of the spine.System 10 is comprised of a bone plate 20, two screws 34, and blockers80. In a more preferred embodiment, the system also includes a blockerfixation element, which may take the form of a cam 66, and a pin 70.Bone plate 20 includes a first pair 32 a of screw holes 26 a and 28 adesigned to receive bone screws 34, and likewise a second pair 32 b ofscrew holes 26 b and 28 b.

It is to be understood that reference numerals pertaining to any onecomponent are also descriptive of additional identical components ofsystem 10, though such numerals may be omitted from the figures forclarity and ease of review. Furthermore, insofar as alternateembodiments are described, it is contemplated that a system may insteadinclude more than one embodiment of a certain component.

Bone plate 20 includes a bottom side 24 and a top side 22, and may beshaped to mount across two vertebrae. Bone plate 20 may possess a firstcurvature along an axis A in its longitudinal plane that allows boneplate 20 to follow the natural lordosis of the section of spine forwhich bone plate 20 is intended. In addition, bone plate 20 may have asecond curvature along an axis B in its transverse plane that allowsbone plate 20 accommodate or to match as closely as possible the shapeof the body of the vertebra or vertebrae to which it is connected. It isto be understood that the opposing ends of bone plate 20 are mirrorimages of one another, with first pair 32 a being located oppositesecond pair 32 b. Bone plate 20 further includes a flat 36 adjacent topside 22 and having a plate hole 98 for accepting pin 70.

In another embodiment similar to FIG. 1, shown in FIGS. 2 and 3, one endof bone plate 120 having flat 136 and pair 132 a is more clearlydepicted, with the other end being a mirror image thereof. Flat 136includes a first side 144, a second side 146, and a rear side 145. Awall 138 substantially surrounds flat 136 at its periphery, and mayprovide an undercut in the form of an angle therewith of less than 90degrees. As such, wall 136 may project over flat 136. Alternatively,wall 138 may form the undercut by being stepped and having an upperportion extending over flat 136. The purpose of the undercut is toprovide a structure on bone plate 120 to mate with and contain blocker80. Flat includes first and second arcuate portions 150 and 152 thatcoincide with the periphery of screw holes 126 a and 128 a,respectively. Flat 136 further includes a projection 148 being disposedbetween screw holes 126 a and 128 a, and a cantilever 154 extending overprojection 148. Cantilever 154 is coplanar with top side 122. Flat 136includes first and second sides 144 and 146 which form first and secondfront ends 158 and 160, respectively, being adjacent to portions of theperiphery of screw holes 126 s and 128 a, respectively. Bone plate 120includes first and second recesses 162 and 164, each being disposedopposite screw hole 126 a and 128 a, respectively, from first and secondfront ends 158 and 160, respectively. As shown in FIG. 3, first recess162 is disposed between flat 136 and cantilever 154, and extends betweenscrew hole 126 a and projection 148. Likewise, second recess 164 issimilarly disposed between flat 136 and cantilever 154, and extendsbetween screw hole 128 a and projection 148.

Cam 66 is depicted in FIG. 1, is mounted on flat 36, and includes afirst cam opening 68 and a second cam opening 72. Pin 70 passes throughfirst cam opening 68 and plate hole 98. Ends of pin 70 may preferably beflared to rotatably secure cam 66 to bone plate 20 such that cam 66 mayrotate about pin 70. Second cam opening 72 is designed to receive adriver in order to rotate cam 66. Both cams 66 depicted in FIG. 1 areshown in an closed position which is defined as the orientation whereinboth first cam opening 68 and second cam opening 72 are aligned parallelto axis A. Alternatively, an open position of cam 66 is defined as theorientation wherein both first cam opening 68 and second cam opening 72are aligned parallel to axis B. Cam 66 may be moved between open andclosed positions by engaging a driver with second cam opening 72 torotate cam 66 about pin 70.

According to another embodiment, cam 266 is depicted in FIG. 4. Cam 266includes a first notch 269 and a second notch 271 (not shown) disposedon opposite sides thereof. First notch and second notch 271 provide agripping tool an alternate means in order to grasp and rotate cam 266between open and closed positions.

As depicted in FIG. 1, blocker 80 is inserted into flat 36 and isconstructed to act as a spring mechanism with respect to flat 36.Blocker 80 includes first and second arcuate regions 84 and 86 adjacentto and shaped to correspond with screw holes 26 a and 28 a,respectively. First and second outer edges 27 and 29 of blocker 80 aredesigned to slide along front ends 58 and 60, respectively, of flat 36.Arcuate regions 84 and 86 converge to form a central region 88 which isdisposed, at least in part, below cantilever 54. Blocker 80 furtherincludes first and second legs 94 and 96 having respective first andsecond bent portions 95 and 97. Bent portions 95, 97 are flexibly bentat approximately a 90 degree angle, and preferably at an angle that isslightly greater than 90 degrees.

Blocker 80 is designed with respect to flat 36 such that the portions offirst and second legs 94 and 96 disposed closest to cam 66 are pressedagainst wall 38. First and second legs 94 and 96 are biased such that ina resting position, arcuate regions 84 and 86 are disposed to overlapscrew holes 26 a and 28 a, respectively, and corresponding arcuateportions 50 and 52, respectively. When force is exerted on blocker 80via either or both of arcuate regions 84 and 86, blocker 80 is pushedaway from screw holes 26 a and 28 a causing first and second legs 94 and96 to bend. First and second legs 94 and 96 may be replaced by anysuitable structure that would allow blocker 80 to move away from andautomatically spring back toward screw holes 26 a and 28 a uponapplication of a force to blocker 80 and subsequent removal of theforce, respectively. Such a force is typically provided by one or morescrews 34 as same are inserted through screw holes 26 a and/or 26 b.

Blocker 80 may be provided in any suitable color, although preferably adifferent color than any other component of system 10, in order todifferentiate therefrom and to provide visual feedback to the surgeon.Blocker 80 may be comprised of a polymeric material, in which case colorcan be added to the material during manufacture, or alternatively aftermanufacture by paint or the like. Blocker 80 may alternatively becomprised of a rigid biocompatible material, such as metal, wherein thecolor may be added via an anodization process.

Bone screw 34 may either be a fixed-angle or a variable-angle screw. Avariable-angle bone screw 34 may be inserted at an angle to a centralaxis of any of screw holes 26 a, 28 a, etc. Bone screw 34 includes athreaded shank 78 and a head 74 having a shoulder 76 (not shown). Head74 has a screw head recess 55 that is sized to be engageable by aninsertion tool, described below. Screw head recess 55 is depicted asbeing substantially cubic, which is preferable as an associated drivingtool is able to better grip bone screw 34 and provide greater torque. Ofcourse, bone screw 34 could be adapted such that head 74 is engageablewith a standard driving tool, such as a flat-head or Phillips-head screwdriver.

According to another embodiment, FIG. 8 shows an end 90 of a tool 89utilized, for example, for inserting bone screw 34. End 90 has across-section in the shape of a quadrilateral, more specifically arectangle or square. The cross-section of end 90 substantiallycorresponds with the shape of screw head recess 55, as shown in FIG. 1.While end 90 and screw head recess 55 are shown to be substantiallysquare, other non-circular orientations are contemplated, such as atriangle, pentagon, hexagon, star, etc. The substantially squarecross-section of end 90 is preferable as it allows for a secureconnection with bone screw 34 while transmitting a great amount oftorque without stripping the interior of screw head recess 55. End 90includes a width W that is no larger than one dimension of screw headrecess 55. End 90 also includes a length L that may be made slightlylarger then another dimension of screw head recess 55. End 90 mayfurther include a slit 92 which separates end 90 into a first end piece93 a and a second end piece 93 b. Such a construction allows end pieces93 a and 93 b to be pressed towards one another during insertion of end90 into screw head recess 55, thereby causing end 90 to exert an outwardforce on the interior of screw head recess 55 to removably secure screw34 to end 90.

FIGS. 9-12 show various embodiments of a handle 91, 191, 291, 391included on a tool 89, 189, 289, 389, respectively, in accordance withadditional embodiments of the present invention. Handles 91, 191, 291,391 are shaped differently to provide the surgeon with differentconfigurations for comfort and driving purposes. End 90 may be common toeach embodiment of tool 89, 189, 289, 389, with handle 91, 191, 291, 391connected to end 90 via a shaft 92. Tools 189, 289, and 389 each includea pommel 187, 287, and 387 and a pommel rod 185, 285, and 385,respectively. Pommel 187 and pommel rod 185 are rigidly connected, andpommel rod 185 is disposed within handle 189 such that pommel 187 andhandle 189 may each pivot independently about an axis through pommel rod185. Such a configuration is preferable as it allows for pressure to beapplied to pommel 187 in a distal direction while allowing handle 189 tobe pivoted about an axis through pommel rod 185. This provides theability to more securely anchor bone screw 34.

The assembly of system 10 can be seen in FIG. 1. Blocker 80 is insertedinto flat 36 such that the outermost portions of blocker 80 in itsrested state contact wall 38 and are contained by the undercut formedbetween wall 38 and flat 36. Outer edges 27 and 29 of arcuate regions 84and 86 are disposed in recesses 62 and 64. Cam 66 is depicted in itsclosed position where it pushes against blocker 80 and arcuate regions84 and 86 are projected over screw holes 26 a and 28 a, respectively.Blocker 80 is substantially laterally blocked in this position.

In use, bone plate 20, with cam 66 in open position, is placed oververtebrae. Next, screws 34 are advanced one at a time through bone plate20 and into the bone of the respective vertebra using tool 89. As screw34 is advanced through bone plate 20, the head portion of screw 34pushes against the corresponding arcuate region 84, 86 of blocker 80,thereby pushing blocker 80 away from screw holes 26 a and 28 a. Blocker80 may exert a spring force toward screw holes 26 a and 28 a in therange of about one pound, though alternative configurations may provideblockers that exert higher or lower forces. A second driver adapted forfinal tightening may be used to finally tighten screw 34. Once screws 34are properly inserted through bone plate 20, cam 66 is rotated to itsclosed position in order to secure blocker 80 with respect to screwholes 26 a and 28 a.

The force provided by blocker 80 provides the surgeon with a tactilefeedback when inserting screw 34 that will alert the surgeon as to whenscrew 34 has moved distally of blocker 80. Such feedback may include anaudible clicking sound as screw 34 moves past blocker 80. The feedbackmay also be visual, the result of the surgeon observing the position ofthe blocker relative to screw 34. As mentioned above, blocker 80 mayalso be colored to enhance visual feedback. If screw 34 has not beenfully inserted, and therefore has not traveled past the edge of arcuateregion 84, blocker 80 will not close. Further feedback is provided tothe surgeon in that the cam cannot be moved into its closed positionuntil and unless the screw head has been fully inserted, i.e. the screwhead is disposed distally of the blocker.

The above procedure may then be repeated for additional screws 34. Theresult is that blocker 80 may be disposed proximal to screws 34, thoughnot necessarily touching same. As may occur after surgery, one or morescrews 34 may loosen and tend to back out of the bone into which theyare inserted. Any loosening of screws 34 would result same coming intocontact with blocker 80, thereby preventing screws 34 from furtherbacking out. This is repeated for each pair of screws. It would be clearto one skilled in the art that the method of use of bone plates ofdifferent size is similar and does not vary in any significant mannerdue to the size of the plate.

In accordance with another embodiment of the present invention, FIG. 5depicts a two-level bone plate system 310 being comprised of a boneplate 320 and three blockers. Bone plate 320 is similar in constructionto bone plate 20 except that it is longer and may cover three vertebrae.In the middle portion of plate 320, blockers are seen with a third pair332 c of screw holes 326 c and 328 c. Of course, blocker 380 c and thirdpair 332 c are as described above, though included at a middle portionof plate 320 as opposed to at an end thereof.

In another embodiment similar to FIG. 5, shown in FIGS. 6 and 7, a boneplate 420 and a middle thereof, respectively, are shown. By virtue ofbone plate 420 being adapted for use across three vertebrae, it includesa third pair 432 c of screw holes 426 c and 428 c. A three-level plate,a four-level plate, a five-level plate, et cetera will have additionalpairs of screw holes for each additional level and an additional blockerassociated therewith.

FIGS. 13-15 depict an additional embodiment of a two-level bone platesystem 510 having bone plate 520 and two blockers 580. It is noted thateach of FIGS. 13-15 depict one end of bone plate 520 with the oppositeend being a mirror image thereof. As well, any level of bone plate maybe created using this particular configuration, as is discussed above.Bone plate 520 includes central portion 548 being substantially as wideas cantilever 554. Central region 588 of blocker 580 is disposed beneathcantilever 554 at least in its blocking position. Bone plate 580 furtherincludes posts 540 and 541 adjacent screw holes 526 a and 528 a,respectively, for rotatably connecting cams 566 to body 580, preferablythrough a snap fit. Blocker 580 includes two notches 581 and 582 whicheach correspond with a wing 583 of cam 566. In a blocking position,blocker 580 is disposed to overlap screw holes 526 a and 528 a whereinone or both cams 566 are oriented such that wing 583 is engaged withnotch 581 and/or 582. Cams 566 may be rotated by a tool, as describedabove.

FIG. 16 depicts another embodiment as bone plate system 610 including acam 666 having three cam extensions 639. Cam 666 is rotatably connectedto bone plate 620 such that when rotated into a locking position, atleast one cam extension 639 overlaps with each of screw holes 626 a and628 a, thereby preventing screws 34 from backing out.

FIGS. 17 and 18 depict a substantially open position and a substantiallyclosed position of a further embodiment as a one-level bone plate system710. Cam 766 is disposed to substantially cover both screw holes 726 aand 728 a. Cam 766 includes a slide 745 which mates with a groove 743 inbone plate 720, which allows cam 766 to move between the substantiallyopen position (as shown in FIG. 18), and the substantially closedposition (as shown in FIG. 19). Cam 766 includes a break 742 whichallows portions of cam 766 to move with respect to one another as cam766 contacts and moves over screw 34 or, alternatively, a peg 35 asshown in FIGS. 17 and 18.

FIGS. 19 and 20 depict bone plate system 810 in accordance with anotherembodiment. Bone plate 820 includes a knob 847 that engages with aprimary cam hole 849 of cam 866, which takes on a triangular orpie-shaped orientation. Cam 866 is pivotable about knob 847. A bridge861 extends over flat 836 between knob 847 and screw hole 828 a, therebyforming a slot 859. Cam 866 is able to pivot through slot 859 in orderto move into a closed position whereby a portion of cam 866 is disposedinside screw hole 828 a and proximal of an inserted bone screw 34. Cam866 further includes a secondary cam hole 857 which is configured toeither receive a manipulation tool and/or to engage a secondary knobwhich extends from the plate in the recessed area in order to removablysecure cam 866 in its closed configuration.

FIGS. 21-25 depict another embodiment of a bone plate system 910. Boneplate 920 includes first and second flats 936 a and 936 b adjacent screwholes 928 a and 926 a, respectively. A cover 911 includes a flap-likeconfiguration, and anchors into flat 936 a via cam ends 963 and 965.Thus, cover 911 may pivot about an axis through cam ends 963 and 965when attached to bone plate 920. Cover includes a cover slot 912separating a cover leg 913 from a cover body 914. Cover slot 912includes a wide end 915 so as to prevent splitting or cracking of cover911 as cover leg 913 is flexed toward and away from cover body 914during insertion thereof into bone plate 920. Cover body 914 has awindow 916 which may aid a tool in manipulating cover 911. Further,cover 911 includes a cover tab 917 on cover body 914 for mating with aplate tab 918 on bone plate 920. Of course, cover tab 917 couldalternatively be placed on cover leg 913.

FIGS. 22 and 25 depict bone plate system 910 in a closed position withrespect to cover 911 and flat 936 a. Cover tab 917 is disposed distallyof plate tab 918, providing a removably securable fit between same. Insuch a closed position, a screw 34 disposed in screw hole 928 a isprevented from backing out, although it is not necessary or required forcover 911 to contact screw 34 to prevent such backout. FIG. 24 depictsbone plate system 910 in an open position with respect to cover 911. Toopen cover 911 from its closed position, a tool is used to provide alifting force to cover 911 via window 916, wherein cover 911 yields andmoves around plate tab 918. Alternatively, the lifting force may beapplied to the non-anchored end of cover 911.

Of course bone plate system 910 may include a cover/flat configurationfor each bone hole. It is noted that the cover provided for plate hole926 a would be a mirror image of cover 911 as depicted in the figures.

FIG. 26 depicts another embodiment as a bone plate system 1010 havingbone plate 1020 and two covers 1011. Each cover 1011 is disposed tooverlap with a pair 1032 a of bone holes 1026 a and 1028 a. Flat 1036has a rotatable button 1019 which mates with a cover hole 1021 having atleast one cover hole lip 1023. When cover 1011 is disposed against flat1036 of bone plate 1020, cover hole 1021 seats around rotatable button1019, which may then be rotated with respect to the axis of cover hole1021 to engage the at least one cover hole lip 1023. In such aconfiguration, cover 1011 is in a substantially closed position withrespect to bone plate 1020. Rotatable button 1019 may include any typeof tool engaging distal end in order to receive a tool for rotation. Forexample, a standard Philips-head or flat end screwdriver may be used, orany other tool disclosed herein may be used.

Cover 1011 further includes cover legs 1025 a and 1025 b which connectwith pins 1027 of bone plate 1020 so that cover 1011 may pivot withrespect to bone plate 1020. Pins 1027 are disposed within a centralopening 1029 of bone plate 1020.

FIG. 27 depicts another embodiment as bone plate system 1110 includingbone plate 1120, cover slide 1131 a having a transverse end 1131 d beingits widest portion, and tightener 1131 c. Tightener 1131 c is rotatablyconnected to bone plate 1120 and is also disposed through a channel 1131b on cover slide 1131 a. As such, cover slide 1131 a may slide alongbone plate 1120 whereby transverse end 1131 d may be positioned overbone holes 1126 a and 1128 a. Tightener 1131 c may be rotatably securedto bone plate 1120 in order to clamp or tighten cover slide 1131 a withrespect to bone plate 1120.

Another embodiment is depicted in FIGS. 28 and 29 including a two-levelbone plate system 1210. Bone plate 1220 includes cantilever 1254 whichis split into first and second projections 1251 and 1253. Absent frombone plate system 1210 is an iteration of central portion 48 of system10. Instead, bone plate 1220 includes space between first and secondprojections 1251 and 1253 and central region 1288 of blocker 1280. Inthis embodiment, central region 1288 extends more broadly between screwhole 1226 a and 1228 a.

Cam 1266 is shown in FIGS. 28 and 29 as having a round exterior and acam recess 1267 shaped to have substantially the same cross section asscrew head recess 55. Notably, tool 89 designed to mate with screw headrecess 55 may then efficiently be used to also mate with cam recess1267. Cam 1266 further includes a boss 1269 with a thruhole 1271. Boss1269 is rotatingly engageable with plate hole 1298 (not shown) of boneplate 1220.

Cam 1266 further includes a top surface 1275, as shown in FIG. 28, and abottom surface 1277, as shown in FIG. 29. Bottom surface 1277 isconfigured to rest upon blocker 1280 while also being configured toengage with an edge 1287 of blocker 1280. Bottom surface includes acamming surface 1279 having a curved portion 1285. Camming surface 1279may be a ramp such that it progressively extends distally from bottomsurface 1277 along a clockwise direction (as shown in FIG. 29) of curvedportion 1285. As such, as cam 1266 is rotated in a counter-clockwisemanner, curved portion 1285 engages edge 1287 of blocker 1280, therebyblocking blocker 1280 from movement in a direction away from pair 1232 aof screw holes 1226 a and 1228 a.

Alternatively, the whole of camming surface 1279 may extend to a certaindistal distance from bottom surface 1277 such that ram 1279 is the onlyportion of cam 1266 disposed distally of bottom surface 1277. In such aconfiguration, cam 1266 may be rotated such that camming surface 1279 iseither engaged or not engaged with blocker 1280.

FIG. 30 depicts an embodiment of bone plate system 1310 similar to thatdepicted in FIGS. 28 and 29, although cam 1366 includes an alternateconfiguration of screw head recess 1355. Cam further includes camprojection 1399 which extends over blocker 1366 in a closed position.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A bone plate comprising: at least one screw hole having a periphery,the screw hole adapted to receive a bone screw; a blocker having ablocking end for blocking a bone screw from further backout of boneshould the bone screw begin to back out after implantation, the blockerbeing predisposed in a blocking position wherein the blocking end atleast partially overlaps a portion of the screw hole, the blocker beingmoveable from the blocking position by contact with the bone screwduring insertion of the bone screw into the screw hole; and a blockerfixation element having an open orientation at which the blocker canmove from the blocking position and a closed orientation, the closedorientation preventing substantial movement of the blocker from theblocking position; wherein, the blocker fixation element cannot be movedto the closed orientation unless the screw head passes the blocker,thereby revealing that the blocker fixation element is in position toprevent substantial movement of the blocker.